feat: SDK update for version 26.2.0

[ChiragAgg5k]

This PR contains updates to the SDK for version 26.2.0.

What's Changed

• Added: DocumentsDB and VectorsDB services for document and vector database access
• Added: userId, emailHash and name parameters to Avatars.getPhoto()
• Added: cloudflare and resend values to OAuthProvider enum
• Added: auto value to ImageGravity enum
• Updated: X-Appwrite-Response-Format header to 2.0.0

[greptile-apps]

Greptile Summary

This PR updates the Flutter SDK for Appwrite 26.2.0.

• Adds DocumentsDB and VectorsDB services and examples.
• Extends avatar photo lookup parameters and supported enum values.
• Updates the response format header, package metadata, compatibility documentation, and generated tests.
• The latest revision adds ImageGravity.auto and uses it in file-preview examples.

Confidence Score: 5/5

The PR appears safe to merge, with no outstanding actionable findings.

The previously reported compatibility statement is fixed and its thread is resolved. The latest enum addition is publicly exposed and serialized consistently, and no new correctness or repository-rule violation was established.

Important Files Changed

Filename	Overview
lib/src/enums/image_gravity.dart	Adds the auto image-gravity value with the expected wire serialization.
docs/examples/storage/get-file-preview.md	Updates both file-preview examples to demonstrate the new automatic gravity option.
lib/services/documents_db.dart	Introduces the generated DocumentsDB transaction and document APIs.
lib/services/vectors_db.dart	Introduces the generated VectorsDB transaction, document, and vector-query APIs.
lib/services/avatars.dart	Adds user ID, email hash, and name inputs to profile-photo resolution.
README.md	Updates package installation and Appwrite 2.0.x compatibility guidance consistently.

_{Reviews (4): Last reviewed commit: "fix: regenerate with the latest sdk-gene..." | Re-trigger Greptile}